The operators of blast furnaces have been switching to powdered coal injection to reduce the amount of coke necessary for the production of iron from iron ore. With powdered coal injection the air to the blast furnace, known as the blast air, must be enriched with oxygen in order to maintain the blast furnace production rate. A conventional method for enriching the blast air is to mix it with some high purity oxygen, having a purity of about 99.5 mole percent, which is generally available from an air separation which produces the oxygen for use in steel refining operations. Alternatively, lower purity oxygen may be employed to enrich the blast air. In either case, the cost of the oxygen is an important consideration in the economics of the production of the hot metal from the blast furnace.
Accordingly, it is an object of this invention to provide a system for enriching the blast air to a blast furnace with oxygen which is more efficient than heretofore available systems.